Many devices are known for dispensing molten thermoplastic materials, such as the devices described in U.S. Pat. Nos. 3,204,828 and 3,298,572.
Generally, such devices comprise a barrel member having an internal melting chamber which communicates with an outlet opening through a nozzle, and a sleeve with a through opening having one end secured to the barrel member with its through opening communicating with the end of the melting chamber opposite the nozzle. The sleeve is adapted to receive an elongate cylindrical block of solid thermoplastic material which fits closely but with a clearance fit within the through opening in the sleeve, with one end portion of the block in the melting chamber and the other end portion projecting through the sleeve. Means are provided for heating the barrel member to melt the end portion of the block therein, and the device includes a handle positioned so that an operator can grip the handle with the fingers of one hand while pressing the block through the sleeve and into the melting chamber with the thumb of that hand to force molten thermoplastic material out of the melting chamber through the nozzle.
While such devices function effectively, certain problems can arise for the operator of such a device when the outer end of a block of thermoplastic material being pressed into the sleeve of the device is closely adjacent or moves past the outer end of the sleeve. The operator's thumb may be burned by molten thermoplastic material that can extrude back toward the outer end of the sleeve through the clearance space between the block and the inner surface of the sleeve. This can be a particular problem if a block of thermoplastic material having a diameter at the small end of the typical tolerance range for such blocks (e.g., 1.511.+-.0.038 centimeters) is used because of the large clearance space (e.g., over 0.076 centimeters) that will exist between the block and the sleeve (which clearance space is necessary so that the sleeve can also freely receive a block at the large end of the tolerance range).
Another problem can occur after the operator places a second block of thermoplastic material end to end with the block in the sleeve and presses on the outer end of the second block. The operator must hold the second block in place, thus occupying the operator's second hand which may be needed elsewhere such as to manipulate articles to which the molten thermoplastic material is being applied. If the operator does not hold the second block in place and releases the pressure on the second block as must be done to stop the flow of the molten thermoplastic material, or applies pressure in some direction other than axially along the second block before its leading end enters the sleeve, the second block can fall or fly away from the block already in the sleeve, which is inconvenient, distracting, and wasteful of the operator's time.